ServiceNow tool tips can be used to explain a particular button, icon or function, that may not be clear for a user at the first glance. A tool tip appears when you hover over an item that needs explanation after a 2 seconds delay.
Don’t overuse tool tips: most functions of an application should be understandable without explanations.
<button class="sn-tooltip-basic btn btn-default" title="This is some tooltip text" data-toggle="tooltip" data-placement="auto">Hover me for a Tooltip</button>